APPROPRIATE CARE GUIDE

Gestational diabetes mellitus An update on screening, diagnosis, and follow-up

Key messages

www.ace-hta.gov.sgPublished: 28 May 2018

During their first trimester, screen high-risk women for pre-existing diabetes using non-pregnancy glucose thresholds. If results are normal, re-evaluate women for GDM at 24 to 28 weeks of gestation.

At 24 to 28 weeks of gestation, screen all pregnant women for GDM using 3-point 75 g OGTT unless they have pre-existing diabetes.

At 6 to 12 weeks after delivery, reassess glycaemic status for women diagnosed with GDM using 2-point 75 g OGTT.

Screen all women with GDM history for diabetes at least once every three years from then on.

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2

3

4

Gestational diabetes mellitus (GDM) is diabetes first diagnosed in the second to third trimester that is clearly not pre-existing.1 It is associated with higher risk of perinatal complications such as pre-eclampsia, macrosomia, and shoulder dystocia. GDM history is associated with increased lifetime risk of diabetes and cardiovascular disease.2

In Singapore, higher prevalence of obesity and advanced maternal age has contributed to an increase in GDM, which occurs in about 1 in 4 to 5 pregnancies.3,4 Appropriate management with diet, exercise, and/or insulin therapy can lower the risk of developing perinatal complications by up to 58%.5

Managing GDM to improve outcomes

Chapter of EndocrinologistsCollege of Physicians, Singapore

College of Obstetricians and Gynaecologists, Singapore

Academy of Medicine,Singapore

College of Family Physicians,Singapore

It is recommended women at high risk be screened for pre-existing diabetes, before conception or during the first prenatal visit (first trimester) using non-pregnancy thresholds.1

If results are normal, re-evaluate them for GDM at 24 to 28 weeks of gestation.

Women with pre-existing diabetes are at greater risk of adverse outcomes than those with GDM. They require tight glucose control, regular eye checks, and specialist management.1

Screen women without any pre-diabetes or diabetes history at 24 to 28 weeks of gestation using 3-point 75 g OGTT. Re-evaluate high-risk women who had normal test results in their first trimester.

Universal screening is favoured over risk-based screening for GDM because Asians generally have a high prevalence of GDM.4 Apart from detecting more GDM cases, universal screening is also associated with improving maternal and foetal outcomes compared to risk-based screening.6

GDM screening is recommended at 24 to 28 weeks of gestation because this phase coincides with an increase in gestational insulin resistance.

Women are considered to be high risk for diabetes if they:– have a pre-pregnancy BMI of more than 30 kg/m2;– have GDM history;– have a history of polycystic ovary syndrome;– have pre-diabetes history;– have delivered a baby 4 kg and heavier;– are 40 years and older.

Women below 40 can do an online diabetes risk assessment at https://www.healthhub.sg/programmes/dra.

The International Association of Diabetes and Pregnancy Study Group (IADPSG) 3-point diagnostic criteria for GDM using the 75 g OGTT is adopted by many organisations including the World Health Organisation and Singapore's College of Obstetricians and Gynaecologists.7-9 GDM is diagnosed if any of the 3-point diagnostic criteria is met (Table 1).

These criteria are based on findings from the Hyperglycaemia and Adverse Pregnancy Outcomes study, a large-scale observational study that included patients from Singapore.10 Studies have shown that using the IADPSG criteria instead of the 2-point criteria identifies GDM cases with higher risks of adverse pregnancy outcomes, suggesting that the IADPSG criteria may be better in identifying women for appropriate GDM management.11

Table 1. GDM diagnostic criteria

Plasma glucose levels* Previous recommendations Current recommendations

Fasting ≥7.0 ≥5.1

1-hour post-OGTT Not applicable ≥10.0

2-hour post-OGTT ≥7.8 ≥8.5

First trimester

24–28 weeks

Screen women at high risk for undiagnosed pre-existing diabetes

Screen all women for GDM

*All values in mmol/L

Plasma glucose usually reverts to pre-pregnancy levels six weeks after delivery. It is recommended 2-point (fasting and two-hour) 75 g OGTT be performed in women with GDM between 6 to 12 weeks after delivery to reassess glycaemic status using non-pregnancy thresholds.12 The same approach applies to women diagnosed with pre-diabetes or diabetes in their first trimester.

Women with GDM history have a seven-fold lifetime risk of developing diabetes.2 In Singapore, an estimated 4 in 10 women with GDM could develop pre-diabetes or diabetes within five years.13

Lifestyle intervention, including increased physical activity and healthy diet, has been shown to reduce the progression from pre-diabetes to diabetes by 35% over 10 years for women with a GDM history.14 Thus, women with a history of GDM should be advised to adopt a healthy lifestyle and regular screening for diabetes or pre-diabetes at least once every three years from then on.1

More frequent follow-up may be required for women who received insulin during pregnancy or those with risk factors for developing diabetes, such as obesity and a family history of diabetes.1

Post pregnancy Follow-up for women with a history of GDM

Avoiding HbA1c for GDM screening and diagnosis

HbA1c should not be used to screen for or diagnose GDM. It is not sensitive in detecting postprandial hyperglycaemia and is generally lower during pregnancy because of increased red blood cell turnover. Screening GDM with HbA1c has also not been validated locally.

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or:

–

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dial

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or;

–

2-ho

ur p

ost-

pran

dial

<6.

7 m

mol

/L.1

About the Agency

The Agency for Care Effectiveness (ACE) is the national health technology assessment agency in Singapore residing within the Ministry of Health (MOH). ACE develops evidence-based “Appropriate Care Guides” or ACGs to guide a specific area of clinical practice. ACGs are aimed at complementing MOH Clinical Practice Guidelines when these are available, by providing additions and updates as reflected in the evidence at the time of development, and incorporating cost-effectiveness considerations where relevant. The ACGs are not exhaustive of the subject matter. When using the ACGs, the responsibility for making decisions appropriate to the circumstances of the individual patient remains with the healthcare professional. This ACG will be reviewed 3 years after publication, or earlier, if new evidence emerges that requires substantive changes to the recommendations.

Find out more about ACE at www.ace-hta.gov.sg/about

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In citation, please credit the Ministry of Health when you extract and use the information or data from the publication.

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1. American Diabetes Association. Standards of Medical Care in Diabetes. Diabetes Care. 2018.

2. Bellamy L, et al. Type 2 diabetes mellitus after gestational diabetes: a systematic review and meta-analysis. Lancet. 2009.

3. Chong YS, et al. Ethnic differences translate to inadequacy of high-risk screening for gestational diabetes mellitus in an Asian population: a cohort study. BMC Pregnancy Childbirth. 2014.

4. Sacks DA, et al. Frequency of gestational diabetes mellitus at collaborating centers based on IADPSG consensus panel-recommended criteria: the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Study. Diabetes Care. 2012.

5. Hartling L, et al. Benefits and harms of treating gestational diabetes mellitus: a systematic review and meta-analysis for the U.S. Preventive Services Task Force and the National Institutes of Health Office of Medical Applications of Research. Ann Intern Med. 2013.

6. Griffin ME, et al. Universal vs. risk factor-based screening for gestational diabetes mellitus: detection rates, gestation at diagnosis and outcome. Diabet Med. 2000.

7. International Association Diabetes Pregnancy Study Groups. International association of diabetes and pregnancy study groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care. 2010.

8. World Health Organization. Diagnostic criteria and classification of hyperglycaemia first detected in pregnancy. 2013 [cited 20 Mar 2018].

9. College of Obstetricians and Gynaecologists Singapore. Guidelines for the management of gestational diabetes mellitus. 2018 [cited 20 Mar 2018].

10. HAPO Study Cooperative Research Group. Hyperglycemia and adverse pregnancy outcomes. N Engl J Med. 2008.

11. Pan L, et al. Pregnancy outcomes of Chinese women with gestational diabetes mellitus defined by the IADPSG’s but not by the 1999 WHO’s criteria. Clin Endocrinol. 2015.

12. Goh SY, et al. Ministry of Health Clinical Practice Guidelines: Diabetes Mellitus. Singapore Med J. 2014.

13. Chi C, et al. Impact of adopting the 2013 World Health Organization criteria for diagnosis of gestational diabetes in a multi-ethnic Asian cohort: A prospective study. BMC Pregnancy Childbirth. 2018.

14. Aroda VR, et al. The effect of lifestyle intervention and metformin on preventing or delaying diabetes among women with and without gestational diabetes: the Diabetes Prevention Program outcomes study 10-year follow-up. J Clin Endocrinol Metab. 2015.

Expert group

Lead discussants

Dr Claudia Chi (NUHS)

A/Prof Chong Yap Seng (NUHS)

Chairperson

Prof Tan Kok Hian (KKH)

Group members

Dr Goh Su-Yen (SGH)

A/Prof Michelle Jong (TTSH)

Dr Khoo Chin Meng (NUHS)

Dr Phyllis Liauw (Thomson Medical Centre)

A/Prof Lim Su Chi (KTPH)

Dr Ng Lai Peng (SHP)

Dr Desmond Ong (NUP)

Dr Adrian Tan (Healthmark Pioneer Mall Clinic)

A/Prof Tan Lay Kok (SGH)

Dr Teh Kailin (NHGP)

References